xe2x80x9cThis application is a continuation division of international application number PCT/EP00/04689, filed May 23, 2000 (status, abandoned, pending, etc.).xe2x80x9d
The present invention relates to improvements in methods of and in apparatus for manipulating sheets of paper, cardboard, metallic foil, plastic material or the like. More particularly, the invention relates to improvements in methods of and in apparatus for accumulating successive stacks of superimposed sheets on discrete supports in the form of platforms such as pallets or the like. Still more particularly, the invention relates to improvements in methods of and in apparatus for introducing empty supports (hereinafter called platforms or pallets) into and for withdrawing or otherwise removing filled pallets from a stacking station wherein a continuously advancing layer or stream of sheets is converted into a succession of stacks or piles reach containing a preselected number of superimposed sheets and each supported by a discrete pallet.
It is already known to introduce into a stacking station successive empty pallets at intervals which are required to gather on each empty pallet a stack or pile of superimposed sheets or to place onto each introduced empty pallet a fully grown stack of superimposed sheets. Empty pallets must be introduced at a rate and in a manner to ensure that they cannot interfere with movements of preceding pallets at, and with evacuation of preceding (loaded) pallets from, the stacking station.
Successive sheets of a stream or flow of sheets are normally obtained by repeatedly severing a running strip or web of paper, foil or the like and by feeding successive sheets from the severing station to a stacking station. The apparatus at the stacking station is arranged to convert the stream into a succession of discrete stacks each of which contains a predetermined number of superimposed sheets and each of which is supported by a discrete pallet. Filled or loaded pallets must be withdrawn from the stacking station in a manner and at a rate to permit for the introduction of empty pallets in good time to ensure that each introduced empty pallet can receive a growing stack or a fully grown stack following the finished stack on the loaded pallet. Problems which arise in conventional aparatus are attributable, either primarily or exclusively or to a certain extent, to the fact that the stacking apparatus receives or should receive or can receive a continuous (uninterrupted) flow or stream of discrete sheets which are or which can be partly superimposed upon each other. The formations of sheets in a series or flow of partially overlapping sheets are known as imbricated patterns.
German patent application Serial No. 36 16 470 A1 (filed by Martini et al. on May 15, 1986 and published Jun. 26, 1987) discloses a method of and an apparatus for accumulating successive piles of superimposed sheets at a stacking station. The apparatus is intended to ensure a reasonably problem-free evacuation of filled pallets from and a reasonably problem-free introduction of empty pallets to the stacking station. Successive sheets of the imbricated stream of partly overlapping sheets are fed into the stacking station by an endless belt conveyor and are gathered on a descending first pallet in such a way that each preceding sheet is fully overlapped by the next-following sheet. A separating finger is thereupon introduced into the stacking station to overlie the topmost sheet of the completed stack and to be overlapped by the first (lowermost) sheet of the next-following (growing) stack. The inserted finger descends at a speed less than that of the pallet and of the fully grown stack on the pallet to thus cause the formation of a clearance between the topmost sheet of the finished stack and the lowermost sheet of the growing stack. The clearance receives a first clamping jaw and the finger is thereupon withdrawn and lifted to a level above the topmost sheet of the next fully grown stack. The just described sequence of steps is thereupon repeated, i.e., the finger is introduced into the pile of superimposed sheets at a level such that it is located above the number of sheets piled up above the first clamping jaw and required to form a second fully grown stack above the stack below the inserted first clamping jaw (i.e., above the stack on the pallet). The thus inserted separating finger is again caused to descend at a speed less than that of the descending fully grown stack on the pallet. The thus obtained fresh (second) clearance receives a second clamping finger. The second fully grown stack (namely the stack between the two clamping jaws) is thereupon clamped by such jaws in that one of the jaws is moved toward the other jaw.
In a next-following step, the lower clearance is enlarged in that the pallet and the fully assembled stack thereon are lowered so that the lower clearance can receive a table which intercepts the clamping jaw and the (second) stack between the two clamping jaws. This renders it possible to evacuate the pallet and the fully grown stack thereon from the stacking station and to introduce an empty pallet which receives and supports the second fully grown stack, This involves the withdrawal of the table and a lowering of the clamped stack so that the first clamp is immediately adjacent the introduced empty pallet. The second clamp is lifted slighty above and further away from the first clamp to thus release the fully grown second stack. A lowering of the first clamp is not possible because this clamp is immediately adjacent the freshly introduced second pallet. The first clamp is thereupon withdrawn so that the second stack can descend onto the second pallet, the second clamp is withdrawn in a next-following step and the aforedescribed sequence of steps is thereupon repeated in connection with the second pallet, the second stack and a third stack which is being or which has been gathered above the second stack.
A drawback of the just described conventional method and apparatus is that the number of steps to be carried out in connection with the gathering and removal of successive stacks is rather high as well as that the apparatus is bulky and its manipulation must be effected by resorting to a complex control system. Furthermore, the frequency at which filled pallets can be withdrawn from, and empty pallets can be introduced into, the stacking station has a relatively low upper limit.
An object of the invention is to provide a novel and improved method of gathering successive stacks or piles of superimposed sheets at a stacking station and of manipulating the supports (such as platforms or pallets) for the stacks in a manner which is simpler than but at least as reliable as heretofore known undertakings.
Another object of the present invention is to provide a method which can dispense with the step of clamping successively gathered fully grown stacks of sheets between pairs of clamping jaws or the like.
A further object of the invention is to provide a method which can dispense with the step or steps of lifting any parts which are inserted into the accumulation of superimposed sheets at the stacking station.
An additional object of the present invention is to provide a novel and improved apparatus for the practice of the above outlined method.
Still another object of the invention is to provide an apparatus which need not employ clamping jaws for fully grown stacks of sheets at the stacking or gathering station.
A further object of the invention is to provide an apparatus which is simpler, more compact and less expensive than heretofore known apparatus for palletizing stacks of paper sheets or the like.
Another object of the invention is to provide novel and improved means for establishing and varying the dimensions of clearances in the accumulation of superimposed sheets at the stacking station.
An additional object of the invention is to provide novel and improved distancing means for use between the piles of sheets at the stacking station of the above outlined apparatus.
Still another object of the invention is to provide the apparatus with novel and improved means for reliably positioning certain sheets of the accumulation of sheets at the stacking station relative to the parts which are movable into and withdrawable from the stacking station and/or relative to the parts which are fixedly mounted at the stacking station.
A further object of our present invention is to provide a novel and improved method of and a novel and improved apparatus for converting an imbricated stream of large or small sheets of metallic, plastic or other suitable material into a succesion of stacks each of which contains or can contain a desired number of superimposed sheets.
Another object of the instant invention is to provide a novel and improved stack building and manipulating apparatus which can be utilized as a superior substitute for heretofore known apparatus serving to palletize stacks or analogous accumulations of superimposed sheets which can be utilized for the wrapping of various types of commodities as well as for numerous other purposes.
One feature of the present invention resides in the provision of a method of supplying platforms (such as pallets) for stacks of a series of succesive sheets of paper, cardboard, metallic foil, plastic material or the like which are supplied to and are superimposed upon each other at a stacking station. The improved method comprises the step of depositing successive sheets of the series upon a first platform at the stacking station to thus accumulate on the first platform a first stack of superimposed sheets. The depositing step can be carried out by resorting to an endless belt conveyor having a upper reach which delivers successive sheets of the series from a source to the stacking station. On their way from the source to the stacking station, the sheets of the series can partially overlap each other and the source can include a device which repeatedly severs a continuous web of sheet material being supplied from a bobbin or the like.
The depositing step includes lowering the first platform with the growing stack thereon and the method further comprises the steps of introducing a stack separating member sideways between the topmost sheet of the first stack and the next-following sheet of the series when the number of sheets in the first stack reaches a preselected number; utilizing the separating member to establish between the topmost sheet of the first stack and the next-following sheet of the series of sheets at the stacking station a gap; inserting a partitioning member between the separating member and the next-following sheet (the lowermost sheet of the growing stack) of the series; withdrawing the separating member from the stacking station so that the next-following sheet of the series (i.e., the lowermost sheet of the then growing stack) is free to descend onto the partitioning member; attracting the next-following sheet to the partitioning member by suction; increasing the width of the gap between the partitioning member and the first stack (this can be readily achieved by moving the first stack and the first platform downwardly relative to the desceding partitioning member); advancing into the thus widened gap a distancing member; evacuating the first stack and the first platform from the stacking station; transporting into the stacking station a second platform beneath the distancing member; removing the distancing member from the stacking station; thereupon interrupting the attracting step; and retracting the partitioning member from the stacking station so that the next-following sheet and the sheets above the next-following sheet (i.e., the growing stack or the lowermost growing stack then located at the stacking station) can descend onto the second platform.
The depositing step can include conveying successive sheets of the series into the stacking station in a predetermined direction transversely of the direction of lowering the stacks of sheets at the stacking station (the conveying step can include advancing successive sheets of the series along a substantially horizontal path which ends at the stacking station), and the introducing step can include moving the separating member into the stacking station by advancing it in the predetermined direction.
The step of increasing the width of the gap can include lowering the first stack at the stacking station at a first speed and lowering the separating member at the stacking station at a second speed which is less than the first speed so that the descending separating member lags behind the descending first platform.
The inserting step can be carried out simultaneously with or can follow the withdrawing step.
The attracting step can include drawing air into openings which are provided in the at least partially hollow partitioning member. Such attracting step normally involves drawing the underside of the next-following sheet of the series (i.e., the underside of the lowermost sheet of the stack which is in the process of growing above the fully grown stack being borne by the first platform) to the upper side of an apertured panel forming part of the partitioning member.
The attracting step can be started upon completed deposition of at least one additional sheet of the series upon the just mentioned next-following sheet. The next-following sheet, the additional sheet and the sheets above the additional sheet (i.e., the sheets of the growing second stack) can be attracted to the partitioning member while the latter descends with but at a speed less than the speed of the first platform and of the fully grown (finished) stack on the first platform.
The depositing step can include propelling successive sheets of the series against a stop at the stacking station so that each sheet which reaches the stop is located at the stacking station, and the method can further comprise the step of temporarily attracting the thus propelled successive sheets to the stop by suction.
The distancing member can comprise a core which is movable into and from the stacking station and a cover which is movable with and relative to the core and includes a portion located between the core and the next-following sheet. The step of advancing the core and the cover of the distancing member into the widened gap can include moving the core into the widened gap and simultaneously moving the core relative to the cover in such a way that the speed of movement of the cover relative to the next-following sheet is zero or at least very close to zero.
The method can further comprise the step of establishing a film of compressed air or another suitable compressed gaseous fluid between the distancing member and the lowermost sheet of the only stack or the lowermost stack then growing at the stacking station.
Another feature of the present invention resides in the provision of an apparatus for supplying pallets or other suitable platforms for a series of successive sheets at a stacking station. The improved apparatus comprises means for conveying to the stacking station a series of successive sheets which are superimposed upon each other on arrival at the stacking station, an elevator which is arranged to suport a platform at the stacking station and to lower the platform thereon at a predetermined speed so that a growing stack of superimposed sheets supplied by the conveying means onto the platform descends therewith at the stacking station, a separating member which is arranged to be introduced into the stacking station between the uppermost sheet of a fully grown stack on the platform and the lowermost sheet of a growing next-following stack, means for lowering the introduced separating member at a speed less than the predetermined speed to thus establish a growing gap between the uppermost sheet of the fully grown stack and the lowermost sheet of the growing next-following stack, a partitioning member which is movable between a first position adjacent to and a second position within the gap as well as downwardly in the gap at a speed less than the predetermined speed to thus further increase the width (height) of the gap, means for temporarily attracting the lowermost sheet of the next-following stack to the partitioning member, and a distancing member which is movable between a first position adjacent to and a second position in the increased gap below the partitioning member.
The conveying means is or can be arranged to supply to the stacking station an at least substantially continuous series of sheets, and the attracting means can include openings provided in the partitioning member and arranged to attract sheets at the stacking station to at least one selected portion of the partitioning member. The partitioning member can include mutually inclined sections. One of the sections has an upper side and the attracting means can further include at least one suction chamber provided in the partitioning member. The aforementioned openings can include suction ports provided in the upper side of the one section of the partitioning means, communicating with the at least one suction chamber and being arranged to attract the underside of the lowermost sheet of the next-following stack at the stacking station. The openings can include ports which are arranged to attract one side of the next-following (growing) stack at the stacking station.
The improved apparatus can further comprise means for urging sheets away from the partitioning member during certain stages of operation of the apparatus, e.g., preparatory to withdrawal of the partitioning member from the gap. Such urging means can be designed in such a way that it includes certain parts of the attracting means. For example, the urging means can include a source of compressed air which is arranged to supply compressed air to openings forming part of the attracting means and provided in the partitioning member.
The distancing member can be provided with openings which confront the underside of the lowermost sheet of the growing stack at the stacking station in the second position of the distancing member, and the apparatus utilizing such distancing member is further provided with means for supplying to the openings of the distancing member compressed air or another suitable compressed gaseous fluid in the second position of the distancing member and/or during movement of the distancing member from the second position to the first position. In accordance with a presently preferred embodiment, the distancing member includes a core which is provided with openings and a cover which overlies the openings of the core and is immediately adjacent the lowermost sheet of the growing stack at the stacking station in the second position of the distancing member as well as during movement of the distancing member from the second position to the first position. The cover is or can be impermeable to fluids. Such apparatus can further comprise means for moving the core and the cover relative to each other so that the speed of the cover relative to the lowermost sheet of the growing stack during movement of the core from its second position to its first position at least approximates zero speed.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and the modes of assembling and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.